Glass composition transparent to ultraviolet light



eta 6, 1936 J. A. M. SMELT 2,056,627

GLASS COMPOSITION TRANSPARENT TO ULTRAVIOLET LIGHT Filed April l4, 1951Smelf,

Patented Oct. 6, 1936 UNITED STATES PATENT OFFICE GLASS COMPOSITIONTRANSPARENT TO ULTRAVIOLET LIGHT Josephus Antonius Maria Smelt,Eindhoven, Netherlands, assignor, by mesne assignments, to GeneralElectric Company, a corporation of New York Application April 14, 1931,Serial No. 530,092 In the Netherlands May 20, 1930 3 Claims. (01.10636.2)

This invention has reference to an ultra-violet parency to ultravioletlight is indicated by way lamp. of example in the following schedule fora wave It is well known that boron-silicate glass free length of 2804 Aand a glass-thickness of 1 mm. from alkali oxide having added to itcalcium 5 fluoride as a flux is transparent to ultra-violet Transparencyto wave A 5 light. These glass mixtures being, however, not(glass-thickness 1 m.) well adapted to be worked up, they are not usedin practice to any appreciable extent. h with addi It has been foundthat even if a fusion contains fg f tion alkali oxide the addition offluoride increases un- NHFHF l0 der certain conditions the transparencyof the resulting glass to ultra-violet light. I gg" P 1 Thus theordinary species of glass in use in the II 11 49 manufacture of glassbulbs can be used after 3 6 g 6 15 addition of fluoride as an envelopefor ultra-violet 15 sources.

Based on the above recognition the invention If a good transparency toWave lengths the has for its object an ultra-violet lamp in whichneighbourhood of 2300 A=deSirei Species o the glass of the bulb containsfluoride and is praca s are pre y u ed in which the content of ticallydevoid of lead, antimony or titane. iron is not higher than 0.1%. 20

In addition it has been found that the quantity The curve in theaccompanying graph shows of fluoride to be added in order to ensure agiven the variation of the transparency to a wave a p y to ultra-Violetlight pends on the length=2804 A of the aforementioned species of choiceof t e t e elementary bodies- This glass II at varying quantities ofadded fluoride.

quantity Should not be large enough to bring On the ordinate are plottedthe percentages of 25 about a trouble f the glass and thus to decreaseultra-violet light transmitted and on the abscissa the transparency toultra-violet light. As fluorthe number f kilograms of NH4FHF added f rides adapted for use according to the invention 00 kilograms of glassThe thickness of t may be mentioned for example Naz SiFs, NH4 glass usedis 1 FHF and KF. What I claim is: 30

The two last-mentioned fluorides are generally A glass for radiatingultrawiolet light com the most pure and for this reason they arepreferisti of substantially 65% S102, substantially a y \lSed- 2% 13203,substantially 5.5% NazO, substantially Examples of 1 9 9 glass adapted 9use 9.5% K20, substantially 15% 38.0, substantially according to theinvention are assembled in the 3% zno mm m traces and a quantity offluoride 5 following Schedule! in the ratio of 1 kilogram of fluoride to100 kilograms of the glass mixture.

eme y bodies I II 111 W 2. A glass for radiating ultra-violet lightconsisting of substantially 67% S102 substantially 2.1% B203,substantially 5.7% NazO, substantially 9.8% K20, substantially 15.4%BaO, iron in traces and a quantity of fluoride in the ratio of 3kilograms of fluoride to 100 kilograms of the glass mixture.

3 3. A glass for radiating ultra-violet light con- 45 ZnO Proportion ofFe calculated as Fe:Oi 0.03 0.03 0.03 0.12 s1st ng of substant ally78.4% $10 substant ally 15.7% B203, substantially 5.1% NazO, substan-The glass mixture I has added to it 1 kilogram tially 0.8% K20, iron intraces and a quantity of of NI-I4FHF and the glass mixtures II, III, andfluoride in the ratio of 3 kilograms of fluoride to IV had added to them3 kilograms of NH4FHF kilograms of the glass mixture.

for 100 kilograms of glass.

The influence 01' these additions on the trans- JOSEPHUS ANTONIUS MARIASMELT.

